Ans. Soft link also called as Symbolic
link. Soft link means link the new file to original file without copying whole
file to new location. And New files size will be the characters in filename of
original file. If you want to get detailed difference then click on next link:
Difference between Soft Link and Hard Link.

4.How to change hostname permanently for server?

Ans. Generally, we are changing hostname
from `hostname command` but this is not the way to change the hostname
permanently. You should have to open the file `/etc/sysconfig/network` and
change the hostname parameter of this file and then restart the network
service.

5.What is the command to convert dos file into
unix format ?

Ans. `dos2unix` command is generally used
for convert dos file into unix format and `unix2dos` command is used to vice
versa.

6.On which port DNS server is running ?

Ans. 53 Port .

7.How to get the lines which matches pattern and 4
lines after the matched pattern ?